Azimuth measuring device



1951 I J. H. DUNAWAY ET AL 2,575,166

AZIMUTH MEASURING DEVICE Filed Dec. 20, 1947 2 SHEETSSHEET 2 Quffl aw/f INVENYTOIIQJI BY M .6

AGENT.

Patented Nov. 13, 1951 7 UNITED QF MEASURING DEVICE" JamesiHJDunawayand Paul BLP oWeII, Houston,

..Tex.,, assignors,..i by mesne assis'nmentsi. to Standard;QilDevelonm nt-Qcm nm El zabeth &.corporat ionof Delaware I V ApplicationDecember 2o, ramsms: No.=-19-2,ess

(eras-4.1.)

' 3.Qla i ms.

:T-he present-invention relates .toageometrical instrument. More particularly: the .inventionlrelates to an azimuth measuring-device suitable for .use'sin navigation and hydrographiczsurveying.

' In navigating .a shipxclosetosho-re. or in hydro..- .graphic' surveying work, it 'iS'OftBILdGSiIELDIG'tO maneuver :a .ship along a predetermined course. Thisis ordinarily done with the' aid of the aships compass. However, .becauseof the varying-effects of winds, tides and local tidal currentsitisnot alwayspossible to maintainthe ship. .on-its:true course with the aid .ofithe compass alone;v Accordingly, itisusual practiceto. fix the bearing and-position of the ship, from time totime, with respect to knowncelestialor terrestrial objects or both; 'This maybe: done with the aid of auxiliary instruments; such; as an azimuth. .circle,. a pe'lorus or; .some instances, asextant.

"These instruments .of the; prior art, however, have certain clisadvantagesewhen used. in hydrographic surveying .or in piloting in closed waters. For example, when surveyingqclose-to vshore as. is often done. in marine geophysical prospecting work, it frequently happens that :the number of "itargetsf or. elevatedIlandmarks of knownixposi- .tionlon -.shore;areL few .andifar. between. Accordv inglypi'n .cases of *thisysort,.;it.-may be .difiicult to fixthe positionxof thetsurveying-ship bymeansof a:sextant.since three targets, preferablvseparatedfromieaehiother at the-pointofiobservation by.- angles in1excess; of; 3.0. degrees; are" required.

With the; apparatus of the present. invention, a

fix maybeobtainediromqonly two;;targets.. If means; such. 3.553;. wire line: or radar, isaavailable tofindicatedistance. insconjunetion with measurements :of; angles; madexwith; a :sextant; a. fix vmav be obtained with .respect. to; two targets. .Only one target is required withthe deviceofthe present invention when: radar or wire line measurementsq'are available.

1 Similarly, when runnin aspecified course simultaneous observations with two" sextants, or two correctedsuccessive observations with. one sextant, are;necessary whereas only a single-observation with .the instrument ofthe presentinvention is necessary.v

.lllthoughv a. pelorusor an azimuth circle is commonly used-toyobtaininformation of the natureeobtainable from the device of the present invention, :ournovel'device has particular ad: vantages over-these devices of thenrior, art. For example, an azimuth circle isgenerally employed directly. with a ship's; compass and consequently is generally not in a position where it maybe slghtedsupon a; target bearin rearwardlyafrom the shipsbridge; Similarlmalthoughthe pelorus is usually fixed ina moreafavorably: locatedipoe sition than is the-ships compass, it is frequently locatedlin sucha manner. thatobjects upon which it is desirable to sight-are. obscured by the. super structure of-theship or some other object; "The device of'the present. invention on the .otherzhand is portable;v and can be readily carriedziand-i used at -will at any point-on aship. The portability of the device of thepresent:inventionmakes-possible the: procurement-of more accurate. .readings than can be obtained 'from'a fixed .pelorousrin roughweather since our novel. device-v may be steadied in the hands of the observer.

The apparatus of the present invention. may bestb-e understcodfrom the accompanying draw-.- ing, irrwhich:

Fig. 1- is aplan viewrof one embodiment 10f the apparatus of our. invention,

'FigsZ is" a side elevation view, partly. insection taken-along the lineIL-II of Fig. 1,

Fig. 3 is another side elevationview, partly in section, taken alongthe line III-4L of :Fig. 2.

Fig. 4 -is. a plan view, partly in section, showing elements: which may be substituted for :certain elements of Fig. 1 in another embodiment :.of:. our invention, and I Fig. 5 -is a schematic diagram .representingisthe electricalicircuit of elementsshown in Fig.- 4.

Referringfirst to' Figs. 1, '2, and 3 the: numeral 1 'il designates .a .fiatbase .plate which isanorma-lly oriented in :a horizontal .planeiwhen the apparathis is inuse and,"forspur.poses:of descriptiomplate ll Will be assumedttobe inia horizontal. plane. A flat' disc .-member 12.: is mountedadjacentyand ina plane aboveand parallel to plate;.l:lxby;means such as ia.bushing l3;having. a-retaining shoulder 13a: anda seating shoulder l;3b-.which. seats against plate .I I 1 aamanner. such; that .1 disc; l2 free .to. rotateabout;its;.center., Bushing l 3 -may.:be;held firmly. in;.,place;:near the, center of plate-,1 I by means of i a. retaining: 1111.11 l4. 01141 11,? under side; thereof; substantiall as illu trated in'..'Fig.'.2.

.Thezuppenface dfgdisc, 1211s. suitably-marked or n raved-withime idian 1ine l5 ofmci ng with a: diameter th reof. The. entir rc mf rence of th sunnersiacerisa sosuit bly marked rs n grayed withiequally spaced: division .l 6; pref ably...cor.re.sponding; to ,eac-hhmfdesree ofa circle Assh wn in rti 1 mark n ac r pon ius to each 1;.0, .--di....sion.:arern e e blrn m er d from 0 to ,180 .thr V ughout: the r.ange.-cn-.-each V h scale, with 10 and-.18 marks-coinc ding I withtlie extremities otthe meridianline. L5,

be driven by a worm gear 3|.

tractor disc |2 may be made to. rotate about bushing 13.

Afiixed to plate adjacent the perimeter of.

disc l2 and upon diametrically opposite sides of the center thereof are two blocks 22 and '23 having marked thereon index line 24 and 25, respectively, which are exactly aligned along a diameter of disc I2.

Preferably, blocks 22 and 23 have" Vernier indicator lines marked thereon as shown adjacent lines 24 and 25 in the drawing. Also affixed to plate adjacent blocks 22 and 23 are sighting members 26 and 21, respectively. Here.- inafter, member 26 may be referred to as the far sight since in use it is .generally farther from the observers eye than is member 21 whichmay be referred to as the near sight. Members 26 and .21 are preferably provided with vertical rigid .wires 26a. and 21a, respectively, aligned in an imaginary plane Which. would be vertical to disc I2 and would include index lines 24 and 25. Members 26 and 21 are also preferably provided with horizontal rigid wires 26b and 21b which may be in an imaginary plane parallel to the upper surface of disc l2. 1 v

Although members 26 and 21 have been illustrated as provided with vertically and horizontally oriented cross wires, it will be understood that other equivalent means may be substituted. Thus, members 26 and 21 may be, arranged as conventional peep sights.v However, as will appear subsequently from a descriptionof the manner of usingthe device of thisinvention, if horizontal. indicia 26b and 21b are omitted, other means such as aspirit level may be, suitably mounted .upon plate H to indicate horizontal orientation thereof.

Passing through bushing l3 along the central axisrthereof and perpendicular to disc I2 is a shaft 28 having rigidly affixed to the upper end thereof a flat member 29 defining an index .290 which lies upon a radial line perpendicular to shaft 28. While member 29- has been-shown in the drawing as an elongated arm, it is to be understood that member 29 may, if desired, be a suitable disc or plate having, adjacent protractor scale markings |6, a suitable index line 29a which lies along one radius thereof. So that accurate readings may be made, a Vernier scale corresponding to each 5 minutes of a circle is preferably provided adjacent index 29a shown in Fig. 1. Since in a practical embodiment of the invention such as is shown in Figs. 1 and 4, no line might-actually bedrawn upon member 29 along the radius terminating at index means29'a, and since frequent reference will be made hereinafter to a line that could be so drawn, for purposes of description this particular radius will be referred to as radial index line 29b.

The lower end of shaft 28 is preferably afiixed to a gear 30 which is arranged to mesh with and Worm gear 31 is affixed to a shaft 32 rotatably mounted in a bracket 33. Knobs 34 may be affixed to the ends of shaft 32 in order that the latter may be readily turned as desired. Bracket 33 is rigidly mounted ricated from rubber, leather or the like.

4 upon the under side of bracket plate 35 which, in turn, is rotatable about the lower end of bushing l3 in a plane substantially parallel to plate II. In order to control rotatability of bracket plate 35, the latter is preferably provided with a resilient brake member 36 which may be fab- Con veniently, member 36 may be affixed to a spring loaded ram 31 which is held in position on bracket arm 35 by retainer 38 containing spring 39. A knob 40 is preferably provided upon the shaft of ram 31 so that brake 36 can be disengaged from contact with plate I By reference to the foregoing description and the drawing it will be seen that, by disengaging brake 36, bracket arm 35 may be rotated freely upon bushing l3. However, since worm gear 3| is bracketed to arm 35 and is also engaged with gear 39 which, in turn, is connected to member 29 by means of shaft28, any rotation ofarm 35 causes identical rotation of member 29. Likewise it will be seen that, when brake 3B is engaged so that arm 35 does not move, rotation of knob 34 and worm gear 3| causes rotation of gear, shaft 28, and member 29 relative to plate II. In other words, movement of member 35 can beused for coarse or rapid positioning of member 29 and radial index line 29?) while rotation of knob 34 can be employed for fine adjustment of the positioning.

In the embodiment of our invention illustrated in Figs. 1, 2 and 3, a thin, polished vane 4| is securely affixed to member 29 along the radial index line 29b in such a manner that vane 4| forms a plane which is perpendicular to disc l2. Vane 4| is preferably constructed of highly polished metal which is thin but rigid enough to withstand reasonable handling without liability of bending. Although its dimensions are not critical, vane 4| is preferably of suflicient length so that it may be mounted with one end adjacent the circumference of disc l2 and with the other end adjacent thecenter of disc l2. Its width should preferably be such that it does not obstruct vision along a line from the junction of indices 21a and 21b to the junction of indices 26a and 261:.

As will become clear from subsequent description of the method for using the device of the present invention, vane 4| is responsive to illumination from, and serves as an aligning means for indicating precise alignment of the radial index line 2% with the azimuth of, a major celestial body such as the sun, or in some instances, the moon. The outer end of vane 4| may in itself serve as index means 29a in conjunction with marks I6 to indicate the relative position of radial index line 291) with respect to meridian line 15 and index lines 24 and 25.

Turning now to Figs. 4 and 5, a photoelectric or photovoltaic means, which also is responsive to illumination from a major celestial body and which may be employed in-place of vane 4| to indicate alignment of the longitudinal axis of member 29 with respect to a major celestial body, is shown. As mentioned heretofore, Fig. 4 is a plan view, partly in section. I It is to be understood that the embodiment to be described in conjunction with Figs. 4 and 5 employs all of the elements described withrespect to Figs. 1, 2 and 3 except vane 4|. Accordingly, for purposes of simplification of the drawing, none of the elements except member 29 and a portion of disc i2 illustrated in Figs. 1, 2 and 3 has been shown in Fig. 4. z

The numerals 42 and 43 designate substantially ncrease 5 fiat pl fotovoltaics:siirfaces haviiig positive-term mus 4221 and 43a andneg a'tive terminals "band 43b-',- respectively. As will-be-seen from- Figi'4;the photoelectric elements are mounted within" a suitable 4 housing member 44 and housing 44 is secured to member 29- in a-manner such that the surfaces Hand-43 lie in"two inters'ecting planes which define an acute angle. 4 'Ifhey are also-mounted soth'atthe planes are perpendicu la'r' tc disc i2, and radialindex li ne ZSb-bis'ects the acute angle formed by th'e plaries'. Housing-44 may b'e mounted at any desired-point along' ra'dial index line 29b; however, it is preferably mou'njted 'sc that' the intersection of planes defined-by surfaces and 43 will lie' approximately above-the center or dlscl2. 7 Y

-' As is wellknown in"the prior art, photovoltaic surfaces 42 and I 43 when exposed 'to-Iigm'ener'gy generate-direct current pctentialsand form cells having 1 positiveand negative terminals 42a, 4321, and 42b, 4322, respectively. In accordancewith one embodiment of'our invention, negative terminals 42band 4Sb may be connected together by a conductor 45. Positive terminals 42a and 43a may be connected by flexible conductors 46 and 41; respectively, to a sensitive galvanometer 48 (see Fig. 5). Meter 48 is preferably of the: type wherein an indicatingpointer registers zero deflection substantially in the middle of a graduated scale and may register deflection upon either side of the-null point depending upon the'direction of flow of current through the meter; By "connecting photovoltaic surfaces 42 and to meter 48 in oppositionto each other as described above; it will 43 receive equal illumination, the indicating pointer of galvanometer 48 will not be deflected. On the other hand, if one photovoltaic surface receives greater illumination than the other, the galvanometer pointer will be deflected. In using the device of our invention member 29 is rotated so that surfaces 42 and 43 are directed toward a luminous, major celestial body and receive equal illumination therefrom as indicated by a null reading upon meter 48. Provided cells 42 and 43 have been suitably compensated electrically, if necessary, index 29a will indicate, in conjunction with the marks upon the circumference of disc l2, the bearing of the celestial body with respect to disc l2.

It will be apparent that meter 48 may be placed in any convenient location with respect to base plate i In a preferred embodiment (not shown in the drawing), however, meter 48 is mounted upon plate I I adjacent far sight 26 where its scale is readily seen when the device of the invention is in use.

To illustrate the method of using the device of the present invention let it be assumed that it is desired to determine the bearing of a ship's course with respect to a fixed terrestrial object which is visible from the ship's deck. The observer holds the plate II at suitable height so that he may align the junctions of cross wires 26a, 26b and 21a, 21b upon the object and at the same time aligns horizontal wires 26b and 21b with the horizon line of the earth. Vane 4| is then adjusted with respect to the sun by suitable movement of arm or knob 34 or both until the vane casts a shadow of minimum width upon member 29 rearwardly of vane 4 I. In conducting this adjustment it will usually be observed that, when one side of vane 4| is oriented slightly across the path of the suns direct rays, a bright streak of light will be reflected rearwardly 01 be apparent thatfif surfaces'42and =vane 4l"onto"dlsci |'2"'or theirearward extensicnzef member; 29. simultaneously. a shadow having a shapeisimilarto the bright .refiectionastreak will also lappear upon :the opposite iside 'of theimem ber-or arm. When vane 4| is further: adjusted intcrperfect 1 paral-l'elism with the patni'sof the sun's-rays, the bright streakand shadow merge into a thin shadow of approximately the sam'e thickness -as vane '4-|'. Vane '41 is henceforthlheld in the I adjusted position byl'braka member '36 in frictional engagement with plate I'I. With-this adj ustment completed, the:- exact time-of day at which -themeasurementwasmade; is notedand the azimuth o f the sun' tor -the par-ticular itime of day, season of the year and fonlatitude oI position is determined from a table such as the well known Hydrographic Ofice publication H71,

required a'ziinuth mark (-as determine'd from the above-mentioned table) f is adjusted i into alignment with vane 4|; The bearing 'ofathe'fixed obj'ect withrespect' to the 'ships course'may'then be-read from the scaleondisc i2 where the lat ter intersects index line 24. v I

If-it-is desired to check thelcourse'wh'ich aship isfollowing with the course which has been-laid out-upon a chart,- disc I2 is first rotated until ".the desired azimuth-of the course with respect-to the 'true'poles 'ofthe earth appears ondisc |2=opposite index -line-' 24. "The exact 'azimuthof the sun 'for the time of the" particular "day and Iatitude When themea'surement is'to be made is noted from a proper-table in the Hydrographic Office'publication H71, and vane 4| is adjusted by mean's of arm 35 and'kn'ob 34 until the tip-of vane 4| o'r indexumean's 29a points to the I mark on -disc I 2 corresponding to the suns azimuth noted from the table. The observer may then sight along the axis of sight members 26 and 2'! while holding horizontal wires 26b and 21b in parallel relation to the horizon line of the earth and while rotating the entire device, including base plate until vane 4| casts its minimum width of shadow as previously described. With the instrument thus oriented in horizontal position and vane 4| parallel to the path of the suns rays, the sight line between sights 26 and 21 will then be along the desired true course and the observer may readily determine whether or not the ship is proceeding along this predetermined course.

The instrument of the present invention may, if desired, be employed to measure the altitude of the sun or moon above the horizon by orienting base plate H in a vertical plane and parallel to the path of the light rays from the particular celestial object. In order to make this measurement, disc |2 is preferably adjusted until meridian line I5 is aligned with index marks 24 and 25. The observer may then hold the instrument so that normally vertical wires 26a and 27a are horizontal and appear coincident with the horizon line of the earth. Holding the instrument in this position, the observer may adjust knob 34 until the image of the celestial object appears upon the inner end of the upper side of vane 4| in perfect horizontal alignment with the line of "sight from wire 21a to 26a. With vane 4| locked in the thus adjusted position, the angle between vane 4| and meridian line l5 may be read from the position of index 29a over the protractor scale of disc I 2. The angle thus measured, when multiplied by two, expresses the angular elevation of the celestial body above the horizon.

While the device of our invention is particu- 7 larly'useful in navigation and hydrographic surveying, it is apparent also, that it may, also be used in surveying on land. Even though the device may conveniently be held in the observers hands, it will be evident that in certain applications the instrument may also be suitably mounted upon .a portable tripod or other form of pedestal.

Although we have described specific embodiments of the apparatus of our invention and the method of using the same, it will be apparent to workers in the art that other modification -and variations may be made without departing from the. scope of our invention as defined in the appended claims. We claim: 1. An azimuth measuring device comprising a horizontally orientable base plate, a .protractor associated with said plate for indicating horizontal orientation thereof, a member carried by said base plate and mounted for rotation in a plane above and parallel to said disc, said member defining a radial index line perpendicular to the axis of rotation thereof and cooperating with said spaced divisions, means for rotating said 8 member about an axis passing perpendicularly through the center of said disc, and aligning means responsive to illumination from a major celestial body, said aligning means bemg mounted upon said member for indicating precise alignment-of said radial index line with th azimuth of said major celestial body. a

2. An azimuth measuring device in accordance with claim 1 in which the aligning means ineludesa thin vane adapted to reflect solar illumination, said vane being rigidly mounted along said radial index line in a plane perpendicular to said disc.

3. An azimuth measuring device in accordance with claim 1 in which the aligning means includes, two fiat photovoltaic surfaces rigidly mounted upon said member in a manner such that said surfaces lie in two intersecting planes which are perpendicular to the disc and form an acute angle with one another and said radial index line bisects said acute angle.

JAMES H. DUNAWAY. PAUL B. POWELL.

REFERENCES CITED The'following references are of record in the file of this patent:

UNITED STATES PATENTS .Number Name Date 335,647 Spencer Feb. 9, 1886 1,942,604 Kennedy Jam-9, 1934 2,099,772 Seidelhuber Nov. 23, 1937 2,155,402 Clark Apr. 25, 1939 2,440,827 Marean et al May 4, 1948 

